排序方式: 共有52条查询结果,搜索用时 171 毫秒
1.
以金属In、SnCl_4·5H_2O为原料、尿素为沉淀剂,采用共沉淀法加入(NH_4)_2SO_4,制备出六方相ITO纳米粉体。通过XRD、TEM、四探针电阻仪、荧光光谱仪以及XPS,研究了ITO粉体的晶型、颗粒形貌、电性能以及光性能。结果表明:加入(NH_4)_2SO_4后,ITO粉体形貌由类菱面体和类球形混合体转变为类球形;不加(NH_4)_2SO_4时晶型为立方相结构,当(NH_4)_2SO_4与铟的物质的量之比为1∶3.45和1∶1.73时粉体晶型转变为六方相结构,继续添加(NH_4)_2SO_4晶型又转变为立方相结构。立方相ITO粉体的电阻率较低为0.64Ω·cm,六方相ITO粉体在相同激发波长下,发射光强度相对较高。 相似文献
2.
Li Li Wang XiaochunWei xiantao Chen YonghuGuo Changxin Yin Min 《Physica B: Condensed Matter》2011,406(3):609-613
Lutetium oxide nanopowders codoped with Tm3+ and Yb3+ were synthesized by the reverse-strike co-precipitation method. Effects of precipitant solution pH on the structural, morphological and upconversion luminescent properties of Lu2O3:2%Yb, 0.2%Tm nanopowders had been investigated. The results show that pH value of the precipitant (NH4HCO3) solution has a significant effect on the particle size, morphology and upconversion emission intensity of the Lu2O3:2%Yb, 0.2%Tm nanopowders. All the samples obtained from different pH value of precipitant solution can be readily indexed to pure cubic phase of Lu2O3, indicating good crystallinity. The upconversion emission intensity of Lu2O3:2%Yb, 0.2%Tm nanopowders obtained from the precipitant solution with pH=11 is the strongest. The enhancement of the upconversion luminescence is suggested to be the consequence of reducing the number of OH− groups and the enlarged nanopowder size. The strong blue, weak red and near infrared emissions from the prepared nanopowders were observed under 980 nm laser excitation, and attributed to the 1G4→3H6, 1G4→3F4 and 3H4→3H6 transitions of Tm3+ ion, respectively. 相似文献
3.
L. Gavrila FlorescuE. Vasile I. SanduI. Soare C. FleacaR. Ianchis C. LuculescuE. Dutu R. BirjegaI. Morjan I. Voicu 《Applied Surface Science》2011,257(12):5270-5273
The work presents preliminary studies with the goal to extend the share of long graphene ribbons in laser-synthesized carbon black. Investigations revealed the existence, as a major constituent, of graphene ribbons composed of up to 10-15 graphene layers, spaced at ∼0.35-0.37 nm and of tens of nanometres in length. The samples used to study the development of this specific structure were obtained from sensitized acetylene-based mixtures and the experiments were performed following the variation of both the experimental parameters and gas composition. 相似文献
4.
Ultrafine MgAl2O4 powder has been synthesized by a polymerized complex method. Heating of a precursor solution containing citric acid (CA), ethylene glycol (EG) and Mg and Al salts with a molar ratio of Mg/Al/CA/EG=1/2/8/32 at 180°C produced a transparent polymeric gel, which have been characterized by FT-IR spectroscopy and TG/DTA. The organic fraction was removed by controlled thermal treatments (350–1200°C) whereby the bimetallic oxide was formed. XRD analysis showed the presence of MgAl2O4 at 600°C. TEM observation showed that the spherical nanosized powders with good uniformity was obtained. Furthermore, these powders showed excellent sinterability, relative density up to 99.8% was achieved when sintered at 1550°C for 3 h in air without any sintering additive. 相似文献
5.
采用阳极弧放电等离子体技术成功制备了各种不同晶粒尺寸的纳米镍粉体材料,并利用X射线衍射(XRD)、透射电子显微镜(TEM)和相应选区电子衍射(SAED)等测试手段对所制备的样品的晶体结构、晶格参数、形貌、粒度进行性能表征. 实验结果表明:阳极弧等离子体法制备的镍纳米粉的晶体结构与相应的块物质相同,为fcc结构的晶态. 不同晶粒尺寸的纳米镍粉体的晶格常数均大于完整单晶镍的晶格常数,晶格畸变表现为晶格膨胀. 晶格常数和晶胞体积随着晶粒尺寸的减小而增大,晶格畸变量与晶粒尺寸的倒数成正比. 镍纳米粉体的晶格膨胀主要是由于受到表面能和表面张力的作用而引起的,可以利用纳米晶体的热力学理论作定性解释.
关键词:
镍纳米粉体
晶格常数
晶格膨胀
晶胞体积 相似文献
6.
Ronaldo Santos da Silva Maria Inês Basso Bernardi Antonio Carlos Hernandes 《Journal of Sol-Gel Science and Technology》2007,42(2):173-179
In this work, we have studied the influence of the pH on the synthesis and structural properties of the Ba0.77Ca0.23TiO3 nanopowders synthesized by a modified polymeric precursor method, in order to achieve non-agglomerated powders. Synthesis,
morphology, thermal reactions, crystallite and average particle size of the synthesized powders were investigated through
thermal analysis (DTA/TG), X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM) and Infrared spectroscopy.
In summary, Ba0.77Ca0.23TiO3 nanopowders were synthesized for the first time at a relative low temperature (500 °C). It was also found that the alkalinity
and acidity of the solution presented a great influence on the powder properties. The best results were obtained from solutions
with pH = 8.5 and 11 whose nanopowders presented weakly agglomerate, with homogeneous particle size and a narrow size distribution
(30–40 nm). This behavior could be explained based on the FT-IR results in which it was possible to see the increased of the
chelation in higher pHs. 相似文献
7.
Intense up-conversion emissions of Yb3+/Dy3+ co-doped Al2O3 nanopowders prepared by non-aqueous sol—gel method 下载免费PDF全文
Li Cheng-Ren Li Shu-Feng Dong Bin Sun Jing-Chang Bo Xiao-Feng Fan Xu-Nan 《中国物理 B》2012,21(9):97803-097803
Yb3+/Dy3+ co-doped Al2O3 nanopowders have been prepared by the non-aqueous sol-gel method and their up-
conversion photoluminescence spectra are measured under excitation by 980-nm semiconductor laser. The results show
that there are comparatively abundant spectra of up-conversion emissions centered at 378, 408, 527 and 543, and 663
nm, corresponding to 4G9/2 → 6H13/2, 4G9/2 → 6H11/2, 4I15/2 → 6H13/2, and 4F9/2 → 6H11/2 transitions of Dy3+,
respectively. Two-photon and three-photon processes are involved in ultraviolet, violet, green, and red up-conversion
emissions. The energy transition between Yb3+ and Dy3+ is discussed. 相似文献
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9.
The spin Hamiltonian parameters (SHPs) and the local structures for impurity W5+ in the Zn3(PO4)2ZnO nanopowders doped with WO3 under different concentrations are theoretically investigated using the perturbation calculations of these parameters. The exponential functions of the related quantities (cubic field parameter Dq, covalency factor N, relative tetragonal compression ratio τ and core polarisation constant κ) of concentration x with totally four adjustable coefficients a, b, c and d are adopted to fit the concentration dependences of the experimental d-d transition bands and SHPs. The impurity W5+ centres demonstrate moderate tetragonal compression ratios τ (~3.1%) due to the Jahn–Teller effect. With the increase of WO3 concentration, Dq and N show moderately decreasing rules, while τ and κ exhibit slightly and moderately increasing tendencies with x, respectively. The mechanisms of the above concentration dependences of these quantities are analysed from the modifications of the local crystal-field strength and electron cloud density around the impurity W5+ with the variation of x. Present theoretical studies would be useful to the exploration of the structural properties and optical applications for WO3 doped Zn3(PO4)2ZnO nanopowders. 相似文献
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