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1.
The TiO2 hollow microspheres were prepared by microwave-assisted solvothermal treatment without template. The morphology and the phase
of TiO2 hollow microspheres were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM),
high resolution transmission electron microscopy (HR-TEM), and BET surface areas. The results show that the particles have
hollow structures and the shell was covered by nanocrystals and have higher specific surface area. The possible formation
mechanism of hollow TiO2 spherical structures has simply been proposed. The activity was evaluated by the photocatalytic degradation of methyl orange
(MO). The results show that the particles having specific surface area show higher photocatalytic activity. It can be attribute
to the doped F atoms and the creation of oxygen vacancies. 相似文献
2.
Wei ZhangShaoyi Jia Qian WuSonghai Wu Jingyu RanYong Liu Jingwei Hou 《Materials science & engineering. C, Materials for biological applications》2012,32(2):381-384
Chitosan-coated magnetite nanocomposites (Fe3O4/CS) were prepared under different external magnetic field by co-precipitation method. The effects of the magnetic field intensity on phase composition, morphology and magnetic properties of the Fe3O4/CS nanocomposites were investigated by X-ray diffractometer (XRD), Fourier transform infrared analysis (FT-IR), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM). The results showed that the intensity of the magnetic field in the co-precipitation reaction process did not result in the phase composition change of the magnetic chitosan but improved the crystallinity of magnetite. The morphology of Fe3O4/CS nanocomposites was greatly changed by the magnetic field. It was varied from random spherical particles to chain-like cluster structure and rod-like cluster structure with the magnetic field intensity increased in the synthetic process. The VSM results indicated that all the products had excellent superparamagnetic properties regardless of the presence or the absence of the magnetic field, and the saturation magnetization values of the Fe3O4/CS nanocomposites were significantly improved by the magnetic field. 相似文献
3.
《Optical Materials》2014,36(12):2618-2623
The uniform hollow spherical Sr2SiO4:Eu2+ green emitting phosphors have been successfully synthesized using hollow silica spheres as templates by an h-BN protective method. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) results directly confirmed the existence of the hollow spherical structure with a narrow size distribution and a shell thickness of 15–25 nm. The h-BN protective film, observed by high resolution TEM, plays an important role in the formation of the hollow spherical morphology and the improvement of photoluminescence properties. Comparing with the Sr2SiO4:Eu2+ micron-phosphor prepared by the traditional solid state reaction method, the hollow spherical phosphor with nano-sized grains exhibits stronger green emission under ultraviolet–blue light excitation. This could be attributed to the elimination of surface defects by the h-BN coating. This research gives an economic and convenient way to synthesize uniform spherical phosphors with high quantum efficiency. 相似文献
4.
ZnO and ZnO-CuO composite hollow spheres were fabricated by using colloidal carbon spheres as templates. The morphology, structure and chemical composition of the as-prepared samples were investigated using field emission scanning electron microscopy, transmission electron microscopy and X-ray diffraction. The photocatalytic activity of the hollow spherical products was evaluated by photocatalytic degradation of methylene blue (MB) aqueous solution at ambient temperature. The results indicated that the ZnO-CuO composite hollow spheres display higher photocatalytic efficiency than pure hollow ZnO products. The related photocatalytic mechanism was discussed based on the microstructure and properties of the ZnO and ZnO-CuO composite hollow spheres. The facile strategy for the preparation of ZnO-CuO hollow nanostructures can be applicable to the synthesis of other composite hollow spheres. 相似文献
5.
Hollow sphere-like Fe3O4 (magnetite) with diameters of between 200-400 nm were synthesized in a reverse microemulsions. The particles were characterized by X-ray powder diffraction (XRD), selected area electron diffraction (SAED), transmission electron microscope (TEM) and field-emission scanning electron microscopy (FESEM). The possible formation mechanism of hollow sphere-like magnetite is discussed. Also, the magnetic properties of the samples were characterized on a vibrating sample magnetometer (VSM). 相似文献
6.
Vongsavat V Vittur BM Bryan WW Kim JH Lee TR 《ACS applied materials & interfaces》2011,3(9):3616-3624
Hollow gold-silver nanoshells having systematically varying sizes between 40 and 100 nm were prepared. These particles consist of a hollow spherical silver shell surrounded by a thin gold layer. By varying the volume of the gold stock solution added to suspensions of small silver-core templates, we tailored the hollow gold-silver nanoshells to possess strong tunable optical extinctions that range from the visible to the near-IR spectral regions, with extinctions routinely centered at ~950 nm. The size and morphology of these core/shell nanoparticles were characterized by dynamic light scattering (DLS), field emission scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM). Separately, X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) were used for measuring their elemental composition; UV-vis spectroscopy was used to evaluate their optical properties. Given their relatively small size compared to other nanoparticles that absorb strongly at near IR wavelengths, these easy-to-synthesize particles should find use in applications that require ultrasmall nanoparticles with extinctions comfortably beyond visible wavelengths (e.g., medicinal therapies, diagnostic imaging, nanofluidics, and display technologies). 相似文献
7.
《Materials Science & Technology》2013,29(6):672-678
AbstractThe morphology and crystallographic phase of V–C carbide particles formed in cast Fe–Cr–Ni–V–C alloys were investigated by means of X-ray diffraction, scanning electron microscopy and transmission electron microscopy (TEM). The combination of results obtained with these techniques revealed that cuboidal, cruciform and spherical carbide particles were formed, depending on the alloy composition, all having the cubic-VC1?x structure (Fm-3m). Detailed TEM observations suggested that small carbide particles were initially cubic in shape and became spherical with increasing particle size. All cuboidal and spherical carbides were single crystallites with no grain boundary at any particle sizes, even after growing to 6 μm in diameter. 相似文献
8.
E.D. Cabanillas 《Materials Letters》2008,62(29):4443-4445
A high-power industrial plasma cutting equipment was applied to carve a SAE 1010 carbon steel. The usually discarded cut material was observed by scanning electron microscopy (SEM) showing that hollow and entire microspheroidal particles were produced. The analysis with X-ray diffraction (XRD) evidenced that the composition of microparticles was FeO, Fe2O3 and Fe3O4. By transmission electron microscopy (TEM) it was found that spherical nanoparticles in the range of 2 to 150 nm in diameter were formed. 相似文献
9.
Atmospheric particles in Seoul, Korea were investigated by scanning electron microscopy (SEM) equipped with energy dispersive X-ray analysis (EDX). Particles were identified and characterized by their morphology and elemental compositions. The morphology of particles was closely coupled with elemental compositions, which provided information on sources and transport processes of aerosols. There were various types of combustion-derived particles identified such as fly ashes, soot, organic matters, tar balls, chars, and sulfur-containing particles. These anthropogenic particles mainly have spherical shape with nano- to micro-meter size. Char was, however, distinguished by irregular shape with varying size up to several micrometers. The sulfur-containing aggregates show a wide range of size, shape, and elemental composition. In addition, bioaerosol and mineral dust were the most abundant particles from natural sources. 相似文献
10.
Naveen V. Kulkarni Soumen Karmakar Srinanadan N. Asthana Ashok B. Nawale Arif Sheikh Shashikant P. Patole J. B. Yoo Vikas L. Mathe Ashok K. Das Sudha V. Bhoraskar 《Journal of Materials Science》2011,46(7):2212-2220
This article addresses the growth of hollow nanocrystalline particles of γ-alumina by the post-oxidation of nano-aluminium
particles in air. The nanoparticles of aluminium were synthesized in a DC-transferred arc thermal plasma reactor. The as-synthesized
nano-aluminium particles were oxidized, in air, at different temperatures. The as-synthesized parent nano aluminium and their
daughter nanoparticles of aluminium oxide were thoroughly characterized with the help of X-ray diffraction analysis, high
resolution transmission electron microscopy and thermogravimetric analysis. Two-step oxidation behaviours, unique in nanoparticles,
are found to be the main driving force behind the formation of hollow spherical structures. The entire phenomenon is compared
with the oxidation behaviour of coarse grain aluminium. The content of γ-alumina, identified by X-ray diffraction, relative
to that of unreacted aluminium, has increased almost exponentially with the oxidation temperature in the case of nano aluminium.
Similar behaviour is not observed in the case of coarse grain aluminium. The crystalline features of alumina, forming the
walls of the hollow sphere, were confirmed by high resolution transmission electron microscopy. 相似文献
11.
12.
Jifen Wu 《Materials Letters》2007,61(21):4332-4335
Tungsten disulfide hollow spherical nanoparticles with diameters of about 100 nm modified by trioctylamine (TOA) have been successfully prepared by a solvothermal process in pyridine. For comparison, WS2 sample was also prepared without TOA modification and sheet-like pieces and their irregular aggregates were obtained. The products were characterized by X-ray power diffraction (XRD), X-ray photoelectron microscopy (XPS), transmission electron microscopy (TEM) and high revolution transmission electron microscopy (HRTEM), respectively. 相似文献
13.
《Materials Characterization》2004,52(3):179-186
Monodisperse and uniformly spherical ZrO2 nanostructured clusters have been synthesized by microwave-assisted sol–gel processing. The techniques used produced molecular-structured precipitates from which zirconia nanometric particles were easily obtained. These particles retained their stability during the subsequent separation process. The microwave treatment was proven to be highly beneficial for assisting the sol–gel processing, mainly because of its contribution to the mixed dispersion and thermal effects. The zirconia nanoclusters thus formed were subsequently characterized by high-resolution electron microscopy to study the nanostructural morphology and transformation defects. 相似文献
14.
Large-size single-crystal Au nanoplates have been successfully prepared by fluorescent light irradiation into the diethyl ether/aqueous solution of HAuCl4 biphasic mixture in the presence of 1,3-diaminopropane (DAP). The products morphology depends on the pH of reaction solution. Au nanoplates were formed at pH below the pKa value of DAP. However, spherical particles were produced under alkaline conditions. These results show that DAP plays a key role in the determination of particle morphology. Properties of the nanoplates were studied by scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. 相似文献
15.
We present a facile solvothermal approach by employing ammonium bicarbonate (NH4HCO3) and ammonium acetate (NH4Ac) as dual gas-bubble-generating structure-directing agent to produce of magnetite (Fe3O4) particles with tunable size ranging from 90 nm to 400 nm and controllable structures including porous and hollow construction. The size, morphology and structure of the final products are achieved by simple adjustment of the molar ratio of NH4HCO3 and NH4Ac, ammonium ion concentration and the reaction time. The results reveal that the molar ratio of NH4HCO3 and NH4Ac strongly influenced the morphology and size of magnetite particles, even could decide the kind of architecture including solid, hollow and porous to form. Particularly, ammonium ion molar concentration plays a significant role in controlling size and magnetic property for magnetite particles. Simultaneously, prolonging the reaction time is beneficial to the magnetite particles growth and inner space escalation with altered reaction time at a certain concentration of ammonium and molar ratio of NH4HCO3 and NH4Ac. Such a design conception of dual gas-bubble-assistance used here is promisingly positive and significant for hollow magnetic particles fabrication and may be extended to other nano-scale hollow construction. 相似文献
16.
T. Prakash R. Jayaprakash C. Espro G. Neri E. Ranjith Kumar 《Journal of Materials Science》2014,49(4):1776-1784
Pure and Sn-doped ZnO nanostructures have been synthesized by the microwave irradiation method. The influence of Sn loading on the morphology and microstructure was evaluated by using field emission scanning electron microscopy, transmission electron microscopy (TEM), energy-dispersive spectrum analysis techniques, X-ray diffraction, and Fourier transform infrared spectroscopy. A change in the growth pattern, from needle-like particles for pure ZnO to agglomerated spherical crystallites for Sn-doped ZnO, has been observed. TEM observations indicated that the average particle size of the pure ZnO nano needles is in the range of 40–60 nm, whereas on addition of Sn spherical nanoassemblies size lies in the range of 10–21 nm. The pure ZnO and Sn-doped ZnO nanostructures were further characterized for their optical properties by UV–Vis reflectance spectra (DRS) and photoluminescence (PL) spectroscopy. 相似文献
17.
Zn/ZnO metal/semiconductor nanostructures were successfully synthesised by a facile zinc-rich chemistry liquid-phase approach with zinc microspheres as sacrificial templates at ambient temperature. A series of globular Zn/ZnO core/shell structures and hollow microsphere architectures self-assembled by Zn/ZnO nanorod heterojunction arrays were obtained by controlling the amount of zinc particles. The structure, morphology, composition and optical properties of the products have been characterised by X-ray diffraction, scanning electron microscopy, Raman spectroscopy and photoluminescent spectroscopy. A possible growth mechanism of the Zn/ZnO nanostructures has been proposed based on the structural analysis. The growth mechanism of Zn/ZnO hollow microspheres is ascribed to Kirkendall effect. A new strong blue emission at 440 nm and a green emission around 500 nm with an enhancement over one order of magnitude compared with the pure ZnO sample have been observed. These emission bands are attributed to two kinds of mechanisms that have been discussed in detail. 相似文献
18.
以CaCl2和Na2CO3为反应原料, 以聚乙烯吡咯烷酮(PVP)和十二烷基磺酸钠(SDSN)为模板剂, 在50℃采用化学沉淀反应, 干燥、煅烧后成功制备了具有微纳分级结构的CaCO3中空微球。采用扫描电子显微镜、透射电子显微镜和X射线衍射等检测手段对所制备的样品形貌、结构进行了表征, 结果显示:所制备的微纳分级结构CaCO3中空微球直径为4~6 μm, 壳壁由直径约60 nm的CaCO3颗粒组成, 壳层厚度约为200 nm, CaCO3中空微球晶相组成为方解石和球霰石的共混体。同时, 在反应温度为50℃、PVP添加量为0.4 g, SDSN浓度为0.1 mol/L的条件下, 所制备的微纳分级结构CaCO3中空微球分散性好, 且形貌比较完整。 相似文献
19.
Hailong Hu 《Materials Letters》2008,62(28):4339-4342
Metallic nickel particles with shapes varying from sea urchin-like to spherical have been selectively synthesized via aqueous chemical reduction. The phase structure and morphology of particles have been investigated by means of X-ray diffraction and scanning electron microscopy. It was found that sodium carbonate greatly accelerated the reduction process to form needle-like dendrites under atmospheric pressure. The probable formation mechanism of the sea urchin-like particles is also discussed. In the mild reduction process, the particle size of nickel nanospheres could be easily controlled by adjusting the experimental parameters. 相似文献
20.
T. Stoyanova Lyubenova F. Matteucci M. Dondi J. Carda 《Materials Research Bulletin》2009,44(4):918-172
Cr-doped CaTiSiO5 was synthesized by spray drying and conventional ceramic method in order to assess its potential as ceramic pigment. The evolution of the phase composition with thermal treatment was investigated by X-ray powder diffraction (XRPD) and thermal analyses (DTA-TGA-EGA). Powder morphology and particle size distribution were analyzed by scanning electron microscopy (SEM) and laser diffraction, respectively. The color efficiency of pigments was evaluated by optical spectroscopy (UV-vis-NIR) and colorimetric analysis (CIE Lab). Results proved that spray drying is an efficient procedure to prepare highly reactive pigment precursors. The spray-dried powders consist of hollow spherical particles with aggregate size in the 1-10 μm range, developing a brown coloration. Optical spectra reveal the occurrence of Cr(III) and Cr(IV), both responsible for the brown color of this pigment. The former occupies the octahedral site of titanite, in substitution of Ti(IV), while the latter is located at the tetrahedral site, where replaces Si(IV). 相似文献